Which statement best reflects the concept of defense in depth?

• A. Use a single firewall at the network edge.
• B. Using multiple overlapping controls across layers.
• C. Rely on antivirus software only
• D. It relies on encryption for all data.

Answer: (B)

Defense in depth means building security from multiple, overlapping protections across different layers so a breach would have to defeat several barriers, not just one. This approach creates redundancy: if one control fails or is bypassed, others still stand in the way, making attacks more difficult and costly. In practice, that means combining defenses at the perimeter and inside the network, protecting endpoints, enforcing strong access controls and authentication (like MFA), encrypting data, and maintaining monitoring and user training. The statement that reflects this idea—using multiple overlapping controls across layers—best captures the concept because it emphasizes layered protections rather than relying on a single mechanism.

Relying on a single firewall at the network edge provides only perimeter protection and can be bypassed. Relying on antivirus software alone covers limited vectors and misses many modern attacks. Relying on encryption for all data protects confidentiality but does not address access controls, detection, or integrity, and can't prevent all kinds of breaches by itself.